Note: The theoretical maximum standard deviation (SD) for a beta distribution (ranging from 0 to 1) is equal to sqrt[mean*(1-mean)]. However, with such a high SD, the beta distribution would have a “spike” of probability density at both its upper and lower bounds.  With a somewhat lower SD, there will only be a spike at the limit closest to the mean.  GoldSim restricts the SD to 0.6 of the maximum theoretical value in order to avoid having any spikes in the density function.  If you need probability distributions that combine discrete spikes with continuous curves, you should construct this explicitly (by combining multiple distributions using an Expression, or by using a Cumulative distribution.